cp's OEIS Frontend

A188237 Number of nondecreasing arrangements of 4 numbers in -(n+2)..(n+2) with sum zero and not more than two numbers equal.

%I A188237 #8 Apr 27 2018 08:31:54
%S A188237 15,30,52,81,121,172,234,311,403,510,636,781,945,1132,1342,1575,1835,
%T A188237 2122,2436,2781,3157,3564,4006,4483,4995,5546,6136,6765,7437,8152,
%U A188237 8910,9715,10567,11466,12416,13417,14469,15576,16738,17955,19231,20566,21960
%N A188237 Number of nondecreasing arrangements of 4 numbers in -(n+2)..(n+2) with sum zero and not more than two numbers equal.
%C A188237 Row 4 of A188236.
%H A188237 R. H. Hardin, <a href="/A188237/b188237.txt">Table of n, a(n) for n = 1..200</a>
%F A188237 Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + 2*a(n-3) - 3*a(n-4) + 3*a(n-5) - a(n-6).
%F A188237 Empirical g.f.: x*(15 - 15*x + 7*x^2 - 15*x^3 + 19*x^4 - 7*x^5) / ((1 - x)^4*(1 + x + x^2)). - _Colin Barker_, Apr 27 2018
%e A188237 Some solutions for n=4:
%e A188237 .-5...-4...-6...-3...-2...-5...-4...-4...-4...-4...-1...-6...-3...-2...-5...-4
%e A188237 .-3....1...-6...-1...-2....0...-1...-1....0...-4....0...-3...-2...-1...-1...-3
%e A188237 ..2....1....6....1....0....0....1...-1....0....4....0....3....2....0....3....2
%e A188237 ..6....2....6....3....4....5....4....6....4....4....1....6....3....3....3....5
%Y A188237 Cf. A188236.
%K A188237 nonn
%O A188237 1,1
%A A188237 _R. H. Hardin_, Mar 24 2011